This CE Center article is no longer eligible for receiving credits.
Impact-Resistant Curtain Walls
A more substantial building envelope system compared to storefronts is a curtain wall system. Commonly, these systems combine aluminum framing with glazing and/or metal panels to hang directly onto the building structural system. Since they are often used on tall buildings, they are subjected to higher wind loads and other conditions. This can be particularly exacerbated during strong wind events, such as hurricanes or tornadoes. Hence, for geographic areas that are prone to such wind events or becoming more likely to experience them, impact-resistant curtain wall systems need to be specified because they are capable of withstanding these severe conditions without failing.
The design of curtain wall systems is a specialty unto itself that combines engineering expertise with material science. Often, curtain wall consultants are brought on board on a project, particularly in the case of free-flowing building designs that require some customization of the manufactured product or the means of attachment. The starting point in all conditions, however, will be determining the specific loading and environmental conditions to which the curtain wall system will be subjected. After that, a review of the standard product offerings of manufacturers can be performed to help determine the best match between a curtain wall system and the specific project needs.
When a resilient building envelope is needed, a hurricane-resistant curtain wall system should be specified. Such systems are engineered to meet the demanding performance requirements present in areas exposed to hurricanes and other forms of severe weather, such as Florida. They often feature shear block assembly with no exposed fasteners, thus creating clean sightlines and maximum installation flexibility. It is also common for these systems to be thermally improved using a continuous thermal spacer interlocked within the horizontal and vertical pressure bar. With U-factors as low as 0.38, these curtain wall systems easily satisfy energy code requirements for overall thermal performance. The glazing in a hurricane-resistant curtain wall typically incorporates an exterior layer of tempered glass and an interior layer of laminated glass (total of 15⁄16 inch), thus providing maximum protection to occupants and property in the event that any of the glass is struck by flying debris or subjected to strong wind forces.
When specifying hurricane-resistant curtain wall systems, there are several performance attributes that should be considered:
- Large and small missile impact and cycling: This is a common testing requirement following established procedures meant to determine how well a product or system can resist impact from flying debris, referred to as “missiles” in the testing language.
- Design pressures: Wind pressure on the surface of the curtain wall system can be positive or negative and is addressed in pounds of pressure per square foot (PSF). To be hurricane resistant, the curtain wall must endure design pressures up to positive 100 PSF and negative 100 PSF.
- Static water resistance: Hurricanes bring heavy rain, and that rain places acute pressure against the building envelope. The recommended criteria in this category is to be able to resist at least 15 PSF of water against the glass and framing.
- Thermal performance: The National Fenestration Rating Council (NFRC) has developed standard methods that combine data on manufactured products with computer simulations to predict thermal performance of curtain wall systems. The manufacturer should have the ability to provide an NFRC rating and bid report for each of its products.
- Codes and standards: Any impact-resistant system used will need to meet the requirements of the building code in the specified project area, including enhanced provisions that exist particularly in Florida and the Texas Gulf Coast. These provisions rely on independent testing following ASTM or similar procedures and recording the results. More stringent code requirements for resilience means the test results may need to be above the average of other locations.
Overall, curtain wall systems need to be looked at and considered for the specific location and the particular needs of the project.
Image courtesy of C.R. Laurence Co., Inc.
Hurricane-resistant curtain wall systems are available to provide greater resiliency in geographic areas prone to severe wind and rain events.
Impact-Resistant Glass Railings
Glass is used in a variety of ways on buildings, and all of it needs to be assessed for its ability to contribute to resilient design. It can be very dangerous if it breaks or shatters on a building, but it is equally problematic if it is used as a guardrail and does not stay in place during a hurricane event. In this scenario, a relatively low-risk condition can escalate if people need to rely on that guardrail during a severe weather event, or if it is damaged and prevents access along a path of travel. In particular, glass railings are often used in locations where a view through the glass is still sought but some wind protection is desired, even in non-storm conditions.
When glass railings are selected to improve resilient design, they need to meet all of the same criteria as other resilient glazing systems. Impact-resistant glass railings are available that are engineered for hurricane-prone regions and incorporate laminated glass. They are made with two layers of glass that are bonded together with an interlayer of either polyvinyl butyral (PVB) or a stronger material with a lower plasticizer content known as ionoplast. Both types of impact-resistant glass railing systems should be tested according to ASTM protocols and have approval for use in Florida and other jurisdictions with more stringent code requirements due to severe weather. Testing and approval includes the base shoe system that holds the glass in place. At least one manufacturer has had its impact-resistant glass railing system tested by the International Code Council Evaluation Service (ICC-ES), which has issued a compliance report (ESR-3842) demonstrating the acceptance. This makes it easier for architects to specify because it will meet building code requirements nationwide.
Impact-resistant glass railing systems do not have to be difficult to install. There are versions that are designed specifically for easy installation and time savings. They do not rely on cementing the glass in the base shoe but use mechanical fastening hardware and tools instead. This type of dry-glaze system makes it easier to place the glass so it self-centers and stays plumb as well. Further, the installation can be done from the occupant side of the railing, eliminating the need for exterior lifts, ladders, or scaffolding. Once in place, if there is ever a need to remove, adjust, or replace the glass panels, the mechanical base shoe system allows this to be done easily by following the manufacturer instructions. This type of glass railing system is designed for both interior and exterior applications and is available in a range of architectural finishes.
Photo courtesy of C.R. Laurence Co., Inc.
Impact-resistant glass railing systems help protect people and property from hurricane weather and remain in place after glass breakage due to a polyvinyl butyral (PVB) or ionoplast interlayer.
Sunshades
One of the ways to make a building more sustainable while addressing resiliency when electric lighting is compromised is to use natural daylighting. There are a variety of techniques available to improve daylighting, but one of the most common methods is to use sunshades over glazing because they also mitigate solar heat gain, particularly during summer months when the sun is higher in the sky. This approach has the advantage of helping to keep the building interior cooler in warm weather while still allowing an ample amount of natural light to enter. In some cases, sunshades can also help protect window openings from falling or flying debris in severe weather events.
Sunshade products are available that use standard parts for economy but can be fully customized to suit the specific needs of a building design. One type is made with perforated aluminum panels that protect building interiors from UV rays and solar heat gain during peak hours, making them ideal for regions with high temperatures. The standard parts consist of stock center, corner, and end panels in both left- and right-hand configurations. This makes them easy to customize and install on buildings. Commonly, they are finished with a powder paint coating. Custom finishes are also available to suit various design needs. Perforated sunshades provide a distinct and appealing aesthetic element that simultaneously improves the sustainability and resilience of the building when used properly.
Photo courtesy of C.R. Laurence Co., Inc.
Perforated aluminum sunshades on buildings help protect interiors from solar heat gain while allowing natural daylight to enter.
Buildings are routinely designed to meet the needs of the local site, average weather conditions, and climate. However, when those local weather and climate conditions change or become more intense than historical data suggests, it is incumbent upon design professionals to adjust building designs accordingly. The fairly recent widespread observance of such changes include an increase in the intensity or quantity of severe weather events such as hurricanes, tornadoes, heavy rain, wind, drought, etc. These conditions are leading to impacts on communities and buildings, including water-related events such as flooding and sea level rise, hot and dry conditions that are literally sparking wildfires around the world, and severe wind events that cause direct damage to buildings and infrastructure.
Photo courtesy of Cascade Architectural
Creating buildings to be resilient so that they can bounce back and be usable following a severe weather event involves making some intentional design decisions on the types of products, materials, and building systems used.
Recognizing severe weather and related events as a design issue is a first step. Determining an appropriate design response is the next. This course looks at some of the basic issues of resilient design and some examples of specific design strategies that can be implemented to create buildings that can remain resilient in the face of increasing changes and challenges.
Defining Resilient Design
Resilience, resilient design, resiliency—these terms seem to get used interchangeably but without a lot of clarity sometimes on what is being talked about. A not-for-profit organization called the Resilient Design Institute (RDI) has done a good job of sorting these out for us. It defines the general term “resilience” as “the capacity to adapt to changing conditions and maintain or regain functionality and vitality in the face of stress or disturbance. It is the capacity to bounce back after a disturbance or interruption.” This is consistent with the way the word resilience is used in general (e.g., resilient flooring “bounces back” after being stressed from foot traffic) and reflects a broad-based understanding. If this quality of resilience is what we seek in our buildings and communities, then it needs to be specifically and intentionally part of the design. Hence, the RDI defines resilient design as “the intentional design of buildings, landscapes, communities, and regions in order to respond to natural and man-made disasters and disturbances—as well as long-term changes resulting from climate change—including sea level rise, increased frequency of heat waves, and regional drought.” In short, it acknowledges that there are specific, identifiable issues that warrant equally specific design responses.
To provide design professionals with some guidance on how to achieve successful resilient designs, the RDI offers a variety of insights and resources, including its 10 Resilient DesignPrinciples available at www.resilientdesign.org.
In addition to RDI, the AIA and other organizations have adopted positions and policy statements on resilient design and offer programs for architects and community leaders. These include the “Reframing Resilience” initiative of the AIA and the Design and Resilience Teams (DARTs) offered through the AIA’s Center for Communities by Design. More information is available on these programs at www.aia.org.
With all of the above in mind, we look next at some specific ways to implement resilient design into buildings. These examples are applicable to all building types in a wide variety of locations and contexts.
Glass and Glazing Systems
For buildings to be resilient enough to survive severe weather and still be functional after an event, the most vulnerable parts of the building must be addressed. This means looking at the entire building envelope, including the roof, walls, and, most notably, glass and glazing systems. The typical approach is seen in news reports of people putting up plywood over windows as a storm approaches. That may work for residential and low-rise commercial buildings, but it is not practical for anything higher than two stories. Furthermore, typical exterior building materials for commercial and institutional buildings are normally not conducive to having plywood nailed or screwed onto them.
Photo courtesy of C.R. Laurence Co., Inc.
High-performance entrance systems provide greater resilience through properly specified components and enhanced thermal properties, all while offering an elegant design using ultra-narrow door stiles.
What is the best approach for most buildings then? To design them with glass and glazing systems that incorporate materials and products that are intentionally fabricated and tested to withstand severe weather conditions, such as high wind loads, airborne debris impact, and/or extreme temperatures. These products can significantly improve the resiliency of buildings. They can also take a variety of forms with some of the more common types discussed in the following sections.
Thermal Entrance Systems
Many commercial, institutional, and industrial buildings incorporate aluminum-framed storefront and glass entrance systems on the first floor. While these are fairly common, there are real differences in the way these types of storefront and entrance products perform. In the case of resiliency, attention should be placed on the specification of the component parts and materials.
A resilient entrance system means that it is strong enough to withstand serious damage from storms while providing superior thermal performance. That way, if the building is occupied, it will help keep the interior environment warm in cold weather and cool in hot weather—a notable benefit at any time, but especially if the building is without power for extended periods.
Achieving this higher level of performance is based fundamentally on three things: the structural and material integrity of the aluminum frame and glass; the insulating value of the system; and the ability to prevent air and water infiltration through the system. Fortunately, there are products available that address all three of these criteria and manage to do so with aesthetic qualities that are appealing and sought after. For example, there are ultra-narrow stile entrance systems available that provide an elegant, all-glass appearance while still delivering exceptional thermal performance normally found in full-frame doors. Excellent thermal performance translates to U-factors as low as 0.33 to help control heat transfer during extreme temperature conditions. This is achieved in part by allowing insulating glass to be used that is 1 inch thick. In addition, such entrance systems meet or exceed the air infiltration requirements of the International Energy Conservation Code (IECC) and ASHRAE 90.1, both of which contain mandatory provisions on this topic.
As a premium storefront product, these entrance systems retain a desirable appearance of heavy glass doors with minimal vertical lines. When it comes to the hardware used for door pulls and panic devices, it is possible to attach them directly to the glass. At least one manufacturer has developed a means to secure such door-pull hardware directly onto 1-inch insulating glass panels using unique through-glass fittings. This provides an added aesthetic and functional benefit without compromising the performance of the doors.
Protecting People and Property
Resilient building design needs to address a variety of potential forces or conditions that can harm people or damage buildings. As already noted, these can include protection from wind-borne debris/missiles but can also include protection against sudden bursts of pressure or even blasts. An alternative to raising the protective performance of individual building envelope components, such as glass and glazing systems, is to protect them with an additional material that is placed on one side or the other. This creative solution is based on using conventional, proven materials in innovative ways.
What type of material would be appropriate here? One choice is coiled wire fabric, which acts like a metal curtain or screening to cover and protect walls, glazing, and entrances in a way that allows a good deal of design flexibility. Coiled wire fabric is often used to provide solar protection and ornamental decoration in buildings. By selecting a grade and type of wire fabric that is appropriately tested, protecting the critical components of a building’s envelope is also possible. Such an approach can help avoid a breach in the envelope that would allow wind and water penetration inside. This can be achieved using coiled wire fabric systems on either the inside or outside of the building enclosure.
For a better understanding of this design concept, let’s now take a closer look at this innovative product.
Coiled Wire Fabric Systems
First, it is important to recognize that coiled wire fabric products are different from traditional metal mesh materials. The essential difference is they are designed as architectural products for use as a finish material, not just a utilitarian one. As a durable, thin material, coiled wire fabric is lighter in weight than traditional wire mesh and offers more design flexibility. For interiors, architects and designers use coiled wire fabric products for window curtains, ceiling treatments, wall coverings, security gates, and even as complete sculpting partitions, all adding elegance and purpose to the spaces where they are used. On building exteriors, they can provide sun shading, fall protection, and visual facade treatments. In all cases, they can allow for ventilation or the controlled passage of air and light.
Photos courtesy of Cascade Architectural
Coiled wire fabric can be used on either the outside or the inside of buildings to provide a variety of attributes, including increased resilient design.
A closer look at the attributes of coiled wire fabric systems follows.
- Material makeup: Coiled wire fabric systems begin with a base metal wire in varieties of steel, aluminum, brass, copper, or stainless steel. The choice of the wire material and its gauge impact the weight, functionality, and aesthetics of the final fabric. By altering the base material, weave thickness, wire gauges, weave pattern, and finishes, the strength, rigidity, and appearance can all be chosen to meet the design or performance characteristics being sought. It is worth noting that the fabric is available in virtually unlimited widths and up to 40 feet in length, so large installations can be achieved with a single panel in many cases. For projects needing more than a 40-foot span of fabric, multiple coils can be spliced together at the job-site in a routine fashion and still create a continuous or seamless appearance.
- Design concepts: Coiled wire fabric is used as a highly decorative design element that adds dramatic and elegant screening to exterior and interior applications. It is highly customizable and available in virtually unlimited finishes. Coiled wire fabric is available in either a natural, uncoated state or with resilient powder-coating finishes for a sharp, long-lasting, durable aesthetic. This means that the color choices are broad, allowing it to be a successful part of virtually any design scheme. Further, the finishes can be specified with low VOC content to protect against that exposure when used on interiors. In fact, some coiled wire fabric products carry Declare labels with the International Living Future Institute.
- Attachment systems: The means of attaching the wire fabric to the building can be done in a variety of ways and with a variety of appearances. The material can be left to hang (i.e., flowing freely), secured at both the top and bottom, or even be pulled taut to create a semi-rigid condition. Because of its fabric nature, curved and undulating shapes are easily achieved, providing facades and interiors with more character and vitality than rectilinear shapes alone. Products are available in either fixed or movable configurations along track attachment systems that are engineered to fit the precise aesthetic and performance requirements of a project. Many attachments are offered in aluminum, steel, or stainless steel and are available with optional ceiling, wall, or suspended mounting systems. Engineered attachment systems can be manufactured flat or undulating to varying degrees, then finished with the coating or color of choice.
- Performance traits: From a resiliency performance standpoint, coiled wire fabric can be used as an element across a full facade in coordination with other building enclosure systems to protect otherwise vulnerable components. In appropriate strengths, it can provide partitioning for safety, fall protection, blast mitigation, and security. As a material added to a building, coiled wire fabric is a long-lasting and durable product requiring minimal if any maintenance. The open nature of the fabric is such that it can be used for solar shading, which can contribute to energy savings. It can also be used for lighting effects (i.e., illuminated with wash lighting) or light diffusion to further enhance the interior ambient lighting of a space.
- Retrofit applications: Coiled wire fabric is light weight making it easy to work into a retrofit or renovation project. This is particularly useful in the case of needing to reinforce and protect facades or other building areas from threats of severe weather or other concerns. The gauge of the wire and the spacing of it will determine the overall strength, which can then be selected to suit a particular retrofit condition.
- Light transparency: The nature of the coiled wire fabric is such that it will allow light to pass through, which is often desirable for many interior design applications. How much light and how visually transparent a certain product appears will be based directly on the makeup of a particular fabric. Those with thicker wires and tighter weaves will obviously allow less light than those with thinner wires and more open weaves. Architects and designers can play with the material’s level of transparency by altering these factors to suit their needs to create a material that is simultaneously open and closed at the desired levels. As such, it is sometimes used over windows, as a diffuser for natural daylight, or as room separators where light is intended to be shared. “Fullness” is another factor that designers can alter that will vary the level of light able to pass through the coiled wire fabric. By using more material than what is required to cover a given area, a billowing drapery effect may be achieved, causing the mesh to overlap which can be used to control the light.
When selecting a coiled wire fabric system for a project, it is important to recognize that there are a lot of different choices in the details of how it can be specified. Manufacturers will readily work with architects and designers to review the specific project requirements and suggest standard options or even engineer a custom solution. Some even offer specific services to support the use of their products, including structural engineering, mechanical engineering, extrusion design, FEA analysis/modeling, drafting, shop drawings, schedules, specifications, fabrication, and on-site installation consultation.
Images courtesy of Cascade Architectural
Coiled wire fabric can be attached to the interior or exterior of a building using a wide variety of available attachment systems.
Testing for Resilience
While all of the foregoing characteristics are appealing for general building use, the question at hand is how well does coiled wire fabric work in terms of resilient design. The University of Ottawa in Ottawa, Ontario, Canada, took on this question in July of 2015. It conducted a series of experiments using a shock-tube apparatus that simulates an explosion or blast and records the intensity of that blast. The shock tube is connected to a chamber that has a test wall constructed on the end. That test wall can then be subjected to a shock wave (blast), and the results of how it reacts can be recorded.
Specifically, the University of Ottawa testing looked at using coiled wire fabric to protect two different wall conditions: an unreinforced masonry (CMU) wall and an aluminum-framed, fixed-glass window. Each wall condition was tested with two different coiled wire fabrics to determine the degree of protection that the fabric did or did not provide during a blast event. The protective coil fabric system had either 14-gauge or 16-gauge wire coils. All wire fabric had a weave size of 3⁄8 inch.
In particular, the testing was performed to see to what degree the wire fabric would contain the fragmentation of either the unreinforced masonry or the glazed windows. In this case, the criteria was to determine the suitability of the fabric according to federal GSA guidelines for blast protection at facilities of the U.S. government. That criteria classifies protection based on measuring how high the debris or fragments of building component (wall, glass, etc.) are thrown above the ground at specified distances out from the facade based on the graph below.
Image courtesy of Cascade Architectural
As shown, the lowest hazard (highest protection) occurs when a blast produces debris that is thrown and falls on the ground no more than 3.3 feet (1 meter) from the blast edge. A low to medium hazard (low to medium protection) exists if the debris falls within 10 feet (3 meters) of the blast site at a height of no more than 2 feet (0.6 meter) above the ground. A high hazard condition (least protection) applies if the debris is thrown 10 feet or more at a height of more than 2 feet (0.6 meter) above the ground.
In the University of Ottawa testing, each test sample was subjected to a single destructive pressure-impulse combination generating high-velocity projectiles. The coiled wire fabric was installed on the unloaded/interior side of the nonstructural walls and windows. The results of each of the four tests indicate that the coiled wire fabric performed well and suffered relatively minor damage that did not impede its intended protective function. The fabric contained the entirety of the unreinforced masonry block walls and prevented potentially life-threatening projectiles from penetrating the test area. It also contained the entirety of the large glass fragments within the first meter of the windows. The pieces of mortar or glass that penetrated the test area were limited to the weave size and did not pose a life safety hazard. As such, they demonstrated the highest level of protection in most cases according to the GSA criteria, with at least a low to medium protection against the smallest fragments that may have passed through. Furthermore, there was no damage observed to the attachment system used to secure the fabric. However, local yielding and uncoiling of wire along some points of the attachment were observed accompanied by minor elongation of the fabric along the vertical centerline. These minor deformations did not compromise the protective qualities of the coiled wire fabric.
Photos courtesy of Cascade Architectural
A series of blast tests were performed on wall and window assemblies with coiled wire fabric covering the outside. In all cases, the fabric performed well and suffered only minor damage.
Overall, coiled wire fabric is shown to provide a protective solution for preventing further building damage and harm to people in severe conditions. It also has the capability to do so in a manner that can be readily integrated with the building design for a cohesive, appealing look.
Impact-Resistant Curtain Walls
A more substantial building envelope system compared to storefronts is a curtain wall system. Commonly, these systems combine aluminum framing with glazing and/or metal panels to hang directly onto the building structural system. Since they are often used on tall buildings, they are subjected to higher wind loads and other conditions. This can be particularly exacerbated during strong wind events, such as hurricanes or tornadoes. Hence, for geographic areas that are prone to such wind events or becoming more likely to experience them, impact-resistant curtain wall systems need to be specified because they are capable of withstanding these severe conditions without failing.
The design of curtain wall systems is a specialty unto itself that combines engineering expertise with material science. Often, curtain wall consultants are brought on board on a project, particularly in the case of free-flowing building designs that require some customization of the manufactured product or the means of attachment. The starting point in all conditions, however, will be determining the specific loading and environmental conditions to which the curtain wall system will be subjected. After that, a review of the standard product offerings of manufacturers can be performed to help determine the best match between a curtain wall system and the specific project needs.
When a resilient building envelope is needed, a hurricane-resistant curtain wall system should be specified. Such systems are engineered to meet the demanding performance requirements present in areas exposed to hurricanes and other forms of severe weather, such as Florida. They often feature shear block assembly with no exposed fasteners, thus creating clean sightlines and maximum installation flexibility. It is also common for these systems to be thermally improved using a continuous thermal spacer interlocked within the horizontal and vertical pressure bar. With U-factors as low as 0.38, these curtain wall systems easily satisfy energy code requirements for overall thermal performance. The glazing in a hurricane-resistant curtain wall typically incorporates an exterior layer of tempered glass and an interior layer of laminated glass (total of 15⁄16 inch), thus providing maximum protection to occupants and property in the event that any of the glass is struck by flying debris or subjected to strong wind forces.
When specifying hurricane-resistant curtain wall systems, there are several performance attributes that should be considered:
- Large and small missile impact and cycling: This is a common testing requirement following established procedures meant to determine how well a product or system can resist impact from flying debris, referred to as “missiles” in the testing language.
- Design pressures: Wind pressure on the surface of the curtain wall system can be positive or negative and is addressed in pounds of pressure per square foot (PSF). To be hurricane resistant, the curtain wall must endure design pressures up to positive 100 PSF and negative 100 PSF.
- Static water resistance: Hurricanes bring heavy rain, and that rain places acute pressure against the building envelope. The recommended criteria in this category is to be able to resist at least 15 PSF of water against the glass and framing.
- Thermal performance: The National Fenestration Rating Council (NFRC) has developed standard methods that combine data on manufactured products with computer simulations to predict thermal performance of curtain wall systems. The manufacturer should have the ability to provide an NFRC rating and bid report for each of its products.
- Codes and standards: Any impact-resistant system used will need to meet the requirements of the building code in the specified project area, including enhanced provisions that exist particularly in Florida and the Texas Gulf Coast. These provisions rely on independent testing following ASTM or similar procedures and recording the results. More stringent code requirements for resilience means the test results may need to be above the average of other locations.
Overall, curtain wall systems need to be looked at and considered for the specific location and the particular needs of the project.
Image courtesy of C.R. Laurence Co., Inc.
Hurricane-resistant curtain wall systems are available to provide greater resiliency in geographic areas prone to severe wind and rain events.
Impact-Resistant Glass Railings
Glass is used in a variety of ways on buildings, and all of it needs to be assessed for its ability to contribute to resilient design. It can be very dangerous if it breaks or shatters on a building, but it is equally problematic if it is used as a guardrail and does not stay in place during a hurricane event. In this scenario, a relatively low-risk condition can escalate if people need to rely on that guardrail during a severe weather event, or if it is damaged and prevents access along a path of travel. In particular, glass railings are often used in locations where a view through the glass is still sought but some wind protection is desired, even in non-storm conditions.
When glass railings are selected to improve resilient design, they need to meet all of the same criteria as other resilient glazing systems. Impact-resistant glass railings are available that are engineered for hurricane-prone regions and incorporate laminated glass. They are made with two layers of glass that are bonded together with an interlayer of either polyvinyl butyral (PVB) or a stronger material with a lower plasticizer content known as ionoplast. Both types of impact-resistant glass railing systems should be tested according to ASTM protocols and have approval for use in Florida and other jurisdictions with more stringent code requirements due to severe weather. Testing and approval includes the base shoe system that holds the glass in place. At least one manufacturer has had its impact-resistant glass railing system tested by the International Code Council Evaluation Service (ICC-ES), which has issued a compliance report (ESR-3842) demonstrating the acceptance. This makes it easier for architects to specify because it will meet building code requirements nationwide.
Impact-resistant glass railing systems do not have to be difficult to install. There are versions that are designed specifically for easy installation and time savings. They do not rely on cementing the glass in the base shoe but use mechanical fastening hardware and tools instead. This type of dry-glaze system makes it easier to place the glass so it self-centers and stays plumb as well. Further, the installation can be done from the occupant side of the railing, eliminating the need for exterior lifts, ladders, or scaffolding. Once in place, if there is ever a need to remove, adjust, or replace the glass panels, the mechanical base shoe system allows this to be done easily by following the manufacturer instructions. This type of glass railing system is designed for both interior and exterior applications and is available in a range of architectural finishes.
Photo courtesy of C.R. Laurence Co., Inc.
Impact-resistant glass railing systems help protect people and property from hurricane weather and remain in place after glass breakage due to a polyvinyl butyral (PVB) or ionoplast interlayer.
Sunshades
One of the ways to make a building more sustainable while addressing resiliency when electric lighting is compromised is to use natural daylighting. There are a variety of techniques available to improve daylighting, but one of the most common methods is to use sunshades over glazing because they also mitigate solar heat gain, particularly during summer months when the sun is higher in the sky. This approach has the advantage of helping to keep the building interior cooler in warm weather while still allowing an ample amount of natural light to enter. In some cases, sunshades can also help protect window openings from falling or flying debris in severe weather events.
Sunshade products are available that use standard parts for economy but can be fully customized to suit the specific needs of a building design. One type is made with perforated aluminum panels that protect building interiors from UV rays and solar heat gain during peak hours, making them ideal for regions with high temperatures. The standard parts consist of stock center, corner, and end panels in both left- and right-hand configurations. This makes them easy to customize and install on buildings. Commonly, they are finished with a powder paint coating. Custom finishes are also available to suit various design needs. Perforated sunshades provide a distinct and appealing aesthetic element that simultaneously improves the sustainability and resilience of the building when used properly.
Photo courtesy of C.R. Laurence Co., Inc.
Perforated aluminum sunshades on buildings help protect interiors from solar heat gain while allowing natural daylight to enter.
Conclusion
Resilient building design is based on some basic principles focused on the intentional actions to recognize and address changing threats to a building. Vulnerable areas, such as glass and glazing systems, can be designed and specified to directly respond to these conditions through high-performance materials and products. An alternative approach is to use protective materials over vulnerable areas that can become an appealing part of the building design. In all cases, the coordinated efforts of all stakeholders in a building will serve to increase the overall resilience of a building following severe events.
Peter J. Arsenault, FAIA, NCARB, LEED AP, is a nationally known architect, consultant, continuing education presenter, and prolific author advancing building performance through better design. www.pjaarch.com, www.linkedin.com/in/pjaarch
